Durable stent graft with tapered struts and stable delivery methods and devices

ABSTRACT

Some embodiments relate in part to endovascular prostheses and methods of deploying same. Embodiments may be directed more specifically to stent grafts and methods of making and deploying same within the body of a patient. Stent embodiments may include tapered struts for an even distribution of strain. Stent embodiments may also include portions which are enlarged in a circumferential direction which may be configured to stabilize the stent in a constrained state.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/799,207, filed Mar. 13, 2013, by D. Parsons et al., titled DurableStent Graft with Tapered Struts and Stable Delivery Methods and Devices,which claims priority under 35 U.S.C. 119(e) from U.S. ProvisionalPatent Application No. 61/620,362, filed Apr. 4, 2012, by D. Parsons etal., titled Durable Stent Graft with Tapered Struts and Stable DeliveryMethods and Devices, each of which is incorporated by reference hereinin its entirety.

FIELD OF THE INVENTION

Some embodiments relate in part to endovascular prostheses and methodsof deploying same. Embodiments may be directed more specifically tostent grafts and methods of making and deploying same within the body ofa patient.

BACKGROUND

An aneurysm is a medical condition indicated generally by an expansionand weakening of the wall of an artery of a patient. Aneurysms candevelop at various sites within a patient's body. Thoracic aorticaneurysms (TAAs) or abdominal aortic aneurysms (AAAs) are manifested byan expansion and weakening of the aorta which is a serious and lifethreatening condition for which intervention is generally indicated.Existing methods of treating aneurysms include invasive surgicalprocedures with graft replacement of the affected vessel or body lumenor reinforcement of the vessel with a graft.

Surgical procedures to treat aortic aneurysms can have relatively highmorbidity and mortality rates due to the risk factors inherent tosurgical repair of this disease as well as long hospital stays andpainful recoveries. This is especially true for surgical repair of TAAs,which is generally regarded as involving higher risk and more difficultywhen compared to surgical repair of AAAs. An example of a surgicalprocedure involving repair of a AAA is described in a book titledSurgical Treatment of Aortic Aneurysms by Denton A. Cooley, M.D.,published in 1986 by W. B. Saunders Company.

Due to the inherent risks and complexities of surgical repair of aorticaneurysms, endovascular repair has become a widely-used alternativetherapy, most notably in treating AAAs. Early work in this field isexemplified by Lawrence, Jr. et al. in “Percutaneous Endovascular Graft:Experimental Evaluation”, Radiology (May 1987) and by Mirich et al. in“Percutaneously Placed Endovascular Grafts for Aortic Aneurysms:Feasibility Study,” Radiology (March 1989). Commercially availableendoprostheses for the endovascular treatment of AAAs include theAneuRx® stent graft manufactured by Medtronic, Inc. of Minneapolis,Minn., the Zenith® stent graft system sold by Cook, Inc. of Bloomington,Ind., the PowerLink® stent-graft system manufactured by Endologix, Inc.of Irvine, Calif., and the Excluder® stent graft system manufactured byW.L. Gore & Associates, Inc. of Newark, Del. A commercially availablestent graft for the treatment of TAAs is the TAG™ system manufactured byW.L. Gore & Associates, Inc.

When deploying devices by catheter or other suitable instrument, it isadvantageous to have a flexible and low profile stent graft and deliverysystem for passage through the various guiding catheters as well as thepatient's sometimes tortuous anatomy. Many of the existing endovasculardevices and methods for treatment of aneurysms, while representingsignificant advancement over previous devices and methods, use systemshaving relatively large transverse profiles, often up to 24 French.Also, such existing systems have greater than desired lateral stiffness,which can complicate the delivery process. In addition, the sizing ofstent grafts may be important to achieve a favorable clinical result. Inorder to properly size a stent graft, the treating facility typicallymust maintain a large and expensive inventory of stent grafts in orderto accommodate the varied sizes of patient vessels due to varied patientsizes and vessel morphologies. Alternatively, intervention may bedelayed while awaiting custom size stent grafts to be manufactured andsent to the treating facility. As such, minimally invasive endovasculartreatment of aneurysms is not available for many patients that wouldbenefit from such a procedure and can be more difficult to carry out forthose patients for whom the procedure is indicated.

What have been needed are stent graft systems and methods that areadaptable to a wide range of patient anatomies and that can be safelyand reliably deployed using a flexible low profile system.

SUMMARY

Some embodiments are directed to a self-expanding cylindrical stentwhich has a constrained state and a relaxed expanded state. The stentmay also include a longitudinal axis, a proximal end, a distal end, anda plurality of resilient struts configured to exert an outward radialforce in the constrained state. At least one of the resilient struts mayinclude a longitudinal section which is enlarged in a circumferentialorientation relative to a longitudinal axis of the stent and configuredto stabilize the at least one strut relative to the position of adjacentstruts while the stent is in a constrained state. At least some of theenlarged longitudinal sections may be in axial alignment with eachother. In some cases, the enlarged longitudinal sections of the strutsmay be enlarged in one transverse dimension of the struts. In somecases, the enlarged longitudinal sections may be enlarged along acircumferential direction about the longitudinal axis of the stent andthe struts may have a substantially constant thickness in a radialdirection relative to the longitudinal axis of the stent. The enlargedlongitudinal section may have an enlarged transverse dimension that isabout 1.5 times to about 3 times the nominal transverse dimension of thestrut in a direction of the enlargement for some embodiments.

Certain embodiments are directed to an endovascular stent graft, havinga main body portion including at least one tubular portion made from atleast one layer of flexible material and a self-expanding cylindricalstent which has a constrained state and a relaxed expanded state. Thestent may also include a longitudinal axis, a proximal end, a distalend, a plurality of resilient struts configured to exert an outwardradial force in the constrained state. At least one of the resilientstruts may include a longitudinal section which is enlarged in acircumferential orientation relative to a longitudinal axis of the stentand configured to stabilize the at least one strut relative to theposition of adjacent struts while the stent is in a constrained state.All resilient struts may include a longitudinal section which isenlarged in a circumferential orientation relative to a longitudinalaxis of the stent and configured to stabilize at least one strutrelative to the position of adjacent struts while the stent is in aconstrained state in some embodiments. In some cases, at least some ofthe enlarged longitudinal sections may be in axial alignment with eachother. In some instances, the enlarged longitudinal sections of thestruts may be enlarged in one transverse dimension of the struts. Insome instances, the enlarged longitudinal sections may be enlarged alonga circumferential direction about the longitudinal axis of the stent andthe struts may have a substantially constant thickness in a radialdirection relative to the longitudinal axis of the stent. The enlargedlongitudinal section may have an enlarged transverse dimension that isabout 1.5 times to about 3 times the nominal transverse dimension of thestrut in a direction of the enlargement in some embodiments.

Some embodiments are directed to a method of loading a delivery cathetersystem with an endovascular stent graft. The endovascular stent graftmay have a main body portion including at least one tubular portion madefrom at least one layer of flexible material, and a self-expandingcylindrical stent which has a constrained state and a relaxed expandedstate. The self-expanding cylindrical stent may include a longitudinalaxis, a proximal end, a distal end, a plurality of resilient strutsconfigured to exert an outward radial force in the constrained state. Atleast one of the resilient struts may include a longitudinal sectionwhich is enlarged in a circumferential orientation relative to alongitudinal axis of the stent and configured to separate and stabilizethe at least one strut relative to the position of adjacent struts whilethe stent is in a constrained state. In some cases, the self-expandingcylindrical stent of the stent graft may be constrained about a bushingof the delivery system such that the enlarged longitudinal section ofthe at least one resilient strut stabilizes the position of the at leastone strut relative to the position of adjacent struts in the constrainedstate. In some instances, the stent may be releasably secured in theconstrained stabilized state.

Some embodiments of an endovascular stent graft may include a main bodyportion having at least one tubular portion made from at least one layerof flexible material and a self-expanding anchor member. Theself-expanding anchor member may include a constrained state, a relaxedexpanded state, a proximal stent portion, and a distal stent portion. Insome cases, the endovascular stent graft may be configured such that aproximal end of the distal stent portion is secured to a distal end ofthe proximal stent portion and a distal end of the distal stent portionis secured to a proximal end of the main body portion. The endovascularstent graft may also be configured such that the axial length of theself-expanding anchor member as a whole divided by the axial length ofthe proximal stent portion is a ratio of about 1.75 to about 2.0.

Some embodiments of a self-expanding anchor member include a constrainedstate, a relaxed expanded state, a proximal stent portion, and a distalstent portion. In some cases, the anchor member may be configured suchthat a proximal end of the distal stent portion is secured to a distalend of the proximal stent portion and the axial length of theself-expanding anchor member as a whole divided by the axial length ofthe proximal stent portion is a ratio of about 1.75 to about 2.0.

Some embodiments of an endovascular stent graft may include a main bodyportion including at least one tubular portion made from at least onelayer of flexible material and a self-expanding cylindrical stent whichhas a constrained state and a relaxed expanded state. The self-expandingcylindrical stent may include a longitudinal axis, a proximal end, adistal end, and a plurality of resilient struts configured to exert anoutward radial force in the constrained state. At least one of theresilient struts may have a longitudinal section which is enlarged in acircumferential orientation relative to a longitudinal axis of the stentand be configured to stabilize the at least one strut relative to theposition of adjacent struts while the stent is in a constrained state.For such an embodiment, all of the resilient struts of the stent mayinclude a longitudinal section which is enlarged in a circumferentialorientation relative to a longitudinal axis of the stent and beconfigured to stabilize the at least one strut relative to the positionof adjacent struts while the stent is in a constrained state. In somecases at least some of the enlarged longitudinal sections may be inaxial alignment with each other. In some instances, the enlargedlongitudinal sections of the struts may be enlarged in one transversedimension of the struts or the enlarged longitudinal sections may beenlarged along a circumferential direction about the longitudinal axisof the stent and the struts may have a substantially constant thicknessin a radial direction relative to the longitudinal axis of the stent.For some embodiments, the enlarged longitudinal section may have anenlarged transverse dimension that is about 1.5 times to about 3 timesthe nominal transverse dimension of the strut in a direction of theenlargement. In some cases, the enlarged longitudinal section includesan undulating configuration of the nominal strut or an oval enlargementof the nominal strut. In some instances, each strut of the stent mayinclude an enlarged longitudinal section with only one enlargedlongitudinal section or an enlarged longitudinal section with aplurality of enlarged longitudinal sections. For some embodiments, thestruts having enlarged longitudinal sections may be disposed in asubstantially longitudinal orientation between the proximal end anddistal end of the stent when the stent is in the constrained state. Insome cases, the struts may be disposed in an undulating pattern. In someinstances, the self-expanding cylindrical stent of the stent graft mayinclude a superelastic alloy such as NiTi alloy.

Certain embodiments are described further in the following description,examples, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an elevation view of an embodiment of an endoluminalprosthesis in the form of a stent graft for treatment of a patient'svessel.

FIG. 1A is an enlarged view of the encircled portion 1A of FIG. 1including a proximal self-expanding stent member and proximal connectorring of the stent graft embodiment of FIG. 1.

FIG. 2 illustrates the stent graft embodiment of FIG. 1 in a constrainedconfiguration disposed on a distal section of a delivery catheter withina lumen of a patient's vessel.

FIG. 3 shows an enlarged view of the encircled portion 3 of the stentgraft of FIG. 2 including the proximal self-expanding stent member in aconstrained configuration but without the constraining releasable beltsfor clarity of illustration.

FIG. 3A is a transverse cross sectional view of the proximalself-expanding stent member and delivery catheter system of FIG. 3 takenalong lines 3A-3A of FIG. 3.

FIG. 4 illustrates the stent graft of FIG. 2 in a deployed unconstrainedstate.

FIG. 5 is a schematic view of an embodiment of a section of a stent thatillustrates features of struts of the stent.

FIGS. 6A and 6AA illustrate paired transverse cross section views of astrut embodiment of FIG. 5 taken along the lines 6A-6A and 6AA-6AA ofFIG. 5.

FIGS. 6B and 6BB illustrate paired transverse cross section views ofanother strut embodiment of FIG. 5.

FIGS. 6C and 6CC illustrate paired transverse cross section views ofanother strut embodiment of FIG. 5.

FIGS. 6D and 6DD illustrate paired transverse cross section views ofanother strut embodiment of FIG. 5.

FIGS. 6E and 6EE illustrate paired transverse cross section views ofanother strut embodiment of FIG. 5.

FIG. 7A illustrates a strut embodiment in longitudinal section takenalong lines 7A-7A of the stent embodiment in FIG. 5.

FIG. 7B illustrates another strut embodiment in longitudinal section.

FIG. 7C illustrates another strut embodiment in longitudinal section.

FIG. 8 illustrates a portion of an embodiment of a stent includingstruts having a stepped taper configuration.

FIG. 9 illustrates a portion of an embodiment of a stent includingstruts having a continuous taper, barbs, and tuck pads with tuck slots.

FIG. 10A illustrates a portion of a cylindrical stent embodiment in aconstrained configuration including struts having coaxial enlargedportion embodiments.

FIG. 10B illustrates a portion of a cylindrical stent embodiment in aconstrained configuration including struts having coaxial enlargedportion embodiments.

FIG. 10C illustrates a portion of a cylindrical stent embodiment in aconstrained configuration including struts having undulating deflectedportions configured to physically separate adjacent struts in acircumferential direction.

FIG. 11 illustrates a portion of a cylindrical stent embodiment in aconstrained configuration shown flattened including struts havingcoaxial enlarged portion embodiments and undulating deflected portions.

FIG. 12 is a transverse cross section view of the stent portion of FIG.11 taken along lines 12-12 of FIG. 11.

FIG. 13 is an elevation view of a bifurcated stent graft embodiment.

FIG. 14 illustrates and embodiment of the stent graft of FIG. 13partially deployed within a patient's aorta.

FIG. 15 is a perspective view of a proximal anchor member embodiment.

FIG. 16 is an elevation view of a cut away portion of the proximalanchor member embodiment of FIG. 15.

FIG. 17 is an elevation view of a cut away portion of the proximalanchor member embodiment of FIG. 16.

FIG. 18 shows a distal portion of the cut away portion of the proximalanchor member of FIG. 16.

FIG. 19 is an enlarged view of the encircled portion 19-19 in FIG. 18.

The drawings illustrate embodiments of the invention and are notlimiting. For clarity and ease of illustration, the drawings are notmade to scale and, in some instances, various aspects may be shownexaggerated or enlarged to facilitate an understanding of particularembodiments.

DETAILED DESCRIPTION

Embodiments of the invention are directed generally to methods anddevices for treatment of fluid flow vessels with the body of a patient.Treatment of blood vessels may be specifically indicated for someembodiments, and, more specifically, treatment of aneurysms, such asabdominal aortic aneurysms. Devices for such treatment modalities mayinclude stents, grafts and stent graft assemblies that include at leastone stent secured to a graft member.

For some embodiments, the modular graft assembly may be bifurcated fortreatment of an abdominal aortic aneurysm. Such a graft assemblyembodiment may include a bifurcated main body member, an ipsilateralgraft extension and contralateral graft extension. The main body mayhave a wall portion that binds a main fluid flow lumen disposed therein.An ipsilateral leg of the main body may have an ipsilateral port and anipsilateral fluid flow lumen that is in fluid communication with themain fluid flow lumen and the ipsilateral port. A contralateral leg ofthe main body may have a contralateral port and a contralateral fluidflow lumen that is in fluid communication with the main fluid flow lumenand the contralateral port. The main body, ipsilateral leg, andcontralateral leg may form a bifurcated “Y” shaped configuration.

For some bifurcated embodiments, the main fluid flow lumen of the mainbody generally may have a larger transverse dimension and area than atransverse dimension and area of either of the fluid flow lumens of theipsilateral leg or contralateral leg. A proximal anchor member may bedisposed at a proximal end of the main body. The proximal anchor membermay include a proximal self-expanding stent that is formed from anelongate element having a generally serpentine shape with four crowns orapices at either end. Each proximal apex or crown of the proximal stentmay be coupled to alternating distal crowns or apices of an eight crowndistal self-expanding stent. The distal self-expanding stent may beformed from an elongate element having a generally serpentine shape. Adistal end of the distal stent may be mechanically coupled to aconnector ring which may be embedded in graft material of the proximalend of the main body, or directly coupled to perforations in theproximal edge region of the main body. Embodiments of the connector ringmay be generally circular in shape having regular undulations about thecircumference that may be substantially sinusoidal in shape. Theproximal stent may include outwardly extending barbs, that may beintegrally formed with the struts of the stent for some embodiments,having sharp tissue penetrating tips that are configured to penetrateinto tissue of an inside surface of a lumen within which the proximalstent is deployed in an expanded state. Although the proximal anchormember may include self-expanding stents, similar stents may be usedthat are configured to be inelastically expanded with outward radialpressure as might be generated by the expansion of an expandable balloonfrom within either or both stents. The connector ring coupled to theproximal stent may also be inelastically expandable.

With regard to graft embodiments discussed herein, such as graftassembly, and components thereof, as well as graft extensions and, theterm “proximal” refers to a location towards a patient's heart and theterm “distal” refers to a location away from the patient's heart. Withregard to delivery system catheters and components thereof discussedherein, the term “distal” refers to a location that is disposed awayfrom an operator who is using the catheter and the term “proximal”refers to a location towards the operator.

FIGS. 1-4 illustrate an embodiment of a stent graft assembly 150 whichmay include a main graft member or main body portion 152 which is notbifurcated. The main body 152 may be tubular in shape and have a wallportion 153 that bounds a main fluid flow lumen 155 disposed therein.The main body 152 may include a proximal end 154, a distal end 156 andan inflatable portion 158. The main body 152 of the stent graft assembly150 may include at least one flexible layer of material such as PTFE,polymer meshes, composites of same or the like. A proximal anchor memberor stent may be disposed at the proximal end 154 of the main body 152.The proximal anchor member embodiment shown in FIG. 1 includes a singleproximal self-expanding stent member 160 disposed about a proximal end154 of the main body 152. In some embodiments, the proximalself-expanding stent member 160 may be formed from an elongate elementhaving a generally serpentine shape with eight crowns or apices ateither end. A distal end 162 of the proximal self-expanding stent member160 may be mechanically coupled to a proximal connector ring 164 whichmay be embedded in graft material generally about the proximal end 154of the main body 152, or directly coupled to perforations in theproximal end 154 region of the main body 152.

A distal self-expanding stent member 170 may be disposed at the distalend 156 of the main body 152 and may be configured to engage an interiorluminal surface 132 within the patient's vasculature 130. The distalself-expanding stent member 170 shown in FIG. 1 includes a singleself-expanding stent member disposed along the distal end 156 of themain body 152 of the stent graft assembly 152. The distal self-expandingstent member 170 may be formed from a resilient elongate element havinga generally serpentine shape with eight crowns or apices at either end.A proximal end 172 of the distal self-expanding stent member 170 may bemechanically coupled to a distal connector ring 174 which may beembedded in graft material generally about the distal end 156 of themain body 152, or directly coupled to perforations in the distal end 156region of the main body 152.

Embodiments of either the proximal connector ring 164 or distalconnector ring 174 may be generally circular or cylindrical in shapewith regular undulations about the circumference that may besubstantially sinusoidal or zig-zag in shape. Some embodiments of eitherthe proximal or distal self-expanding stent members 160, 170 may includeoutwardly extending barbs 165 (see FIG. 1A). Such barbs 165 may beintegrally formed with the struts 168 of either the proximalself-expanding stent member 160 or distal self-expanding member 170.Furthermore, the barbs 165 may have sharp tissue penetrating tips thatmay be configured to penetrate into tissue of an inside surface of alumen within which either the proximal self-expanding stent member 160or distal self-expanding member 170 may be deployed into an expandedstate.

Although the proximal and distal self-expanding stent members 160 and170 of the stent graft 150 has generally been described as includingself-expanding stents, the proximal and distal self-expanding stentmembers 160 and 170 may also include similar stents that are configuredto be inelastically expanded with outward radial pressure as might begenerated by the expansion of an expandable balloon from within eitherthe proximal self-expanding stent member 160 or distal self-expandingstent member 170. Additionally, at least one of the proximalself-expanding stent member 160 and distal self-expanding stent member170 may be made from or include a superelastic alloy, such as NiTialloy.

The stent graft 150 may further include an optional inflation conduit(not shown) which may serve as a fill manifold for inflation of theinflatable portion 158 of the stent graft 150. The inflation conduit mayinclude a distal end with an inflation port in fluid communication withan exterior portion of the main body 152 and extending from the distalend 156 into an interior volume of the inflatable portion 158 of thestent graft 150.

Some embodiments of the stent graft 150 may include radiopaque markers116 that may be used to facilitate alignment of the stent graft 150. Aradiopaque marker 116 configuration and imaging system may be used foralignment during positioning of the stent graft 150 in a patient. FIG.1A illustrates an enlarged view of a portion of the stent graft 150 withportions of the stent graft 150 not shown for clarity of illustration.The stent graft 150 embodiment shown in FIG. 1A illustrates the proximalend 154 of the main body 152, the proximal self-expanding stent member160, and a plurality of radiopaque markers 116 disposed about acircumference of a distal end 162 of the proximal self-expanding stentmember 160. Furthermore, the plurality of radiopaque markers 116 mayinclude helically wound wire members which may be disposed aboutconnector members 216, as shown in FIG. 1A. In general, the connectormembers 216 may be configured to mechanically couple the proximalself-expanding stent member 160 to the proximal connector ring 164disposed within the proximal end 154 of the main body 152 of the stentgraft 150. Some embodiments of the stent graft 150 may additionally oralternatively include a plurality of radiopaque markers 116circumferentially disposed about a tubular portion of the endovascularstent graft 150. For example, the radiopaque markers 116 may lie in aplane that is substantially orthogonal or parallel to a longitudinalaxis 186 of the tubular main body 152 of the stent graft 150.Additionally, the distal self-expanding member 170 may include one ormore radiopaque markers 116.

Furthermore, any number of features may be incorporated into the stentgraft 150 which may enable detection of all or part of the stent graft150 under fluoroscopy or other suitable forms of imaging. For example,in general, the radiopaque markers 116, or other detection features, maybe used to facilitate orthogonal orientation of the imaging axis orview. Once a substantially orthogonal view angle is achieved, anaccurate axial position of the partially deployed stent graft 150relative to the patient's vasculature may be achieved, avoidingparallax, ensuring precise placement of the stent graft 150 relative tosignificant branch vessels or other anatomic reference points. Parallaxin some circumstances may cause error in axial placement of the stentgraft 150 relative to the intended target site. Accurate positioning maybe achieved with axial movement and adjustment of the stent graft 150 bymanual manipulation of a proximal portion of the delivery catheter 100.

As shown in FIG. 2, the stent graft 150 may be positioned such that theproximal end 154 of the main body 152 of the stent graft 150 is aligneddistal of the ostium of the renal arteries. Once the delivery catheter100 system has been positioned at the treatment site an outer sheath 102of the delivery catheter 100 may be proximally retracted. Though theouter sheath 102 may have been proximally retracted, thus exposing thestent graft 150, the stent graft 150 may remain in a partiallyconstrained state with the proximal self-expanding stent member 160restrained by a pair of proximal releasable belts 104 and 106 releasablydisposed about the proximal self-expanding stent member 160. The distalself-expanding stent member 170 may be constrained by another set ofdistal releasable belts 108 and 110 which may be releasably disposedabout the distal self-expanding stent member 170.

Each of the releasable belts 104, 106, 108 and 110 may be configured tobe independently released by retraction of one or more respectiverelease wires 120. Release wires 120 may be disposed within an end loopor loops of the releasable belts 104, 106, 108 and 110 with the one ormore release wires 120 holding the loops in fixed relation to eachother. For this arrangement, retraction of one or more release wires 120from the end loops releases the loops to allow them to move relative toeach other which in turn removes the constraint of the belt members 104,106, 108 and 110 about the respective proximal and distal self-expandingstent members 160 and 170. After at least partial deployment of theproximal stent member 160, finalizing the axial position of the stentgraft 150 relative to the anatomy of the patient's vasculature 130 andtreatment site may then be made. The axial positioning may beaccomplished in some embodiments with the use of one or more radiopaquemarker devices 116, as described above. Once the partially radiallyconstrained stent graft 150 is axially aligned, the proximalself-expanding stent member 160 may then be fully deployed in order toengage and become secured to the luminal wall or interior luminalsurface 132 of the patient's vasculature 130, as shown by way of examplein FIG. 4. Once the proximal anchor member 160 is fully deployed, theinflatable portion 158 of the stent graft 150, including the network ofinflatable channels, may be inflated with a fill material. For someembodiments, the network of inflatable channels may be filled from adesired site within the inflatable portion 158. More specifically, theinflatable portion 158 may be inflated with fill material from aproximal end 154 of the main body 152.

The proximal self-expanding stent member 160 may be disposed at andsecured to a proximal end 154 of the main body 152. For example, theproximal self-expanding stent member 160 may have a first self-expandingstent member 200 secured to a second self-expanding stent member 202.Both the first and second self-expanding stent members 200 and 202 mayhave a somewhat tubular shape and may be secured together by one or morestruts 168. Some embodiments of the struts 168 may have one or morecross sectional areas 169 that vary along the length of the strut 168.Such a configuration may be useful in avoiding points of concentratedstress in, for example, the proximal self-expanding stent member 160 orstruts 168. The proximal self-expanding stent member 160 may include atleast one barb 165 and/or enlarged portion 180 on each strut 168, everyother strut 168 or combinations thereof. One proximal self-expandingstent member 160 embodiment may have a repeated strut 168 pattern havinga more proximally placed barb 165 on one strut 168, an adjacent neighborstrut 168 with a more distally placed barb 165, and a following adjacentstrut 168 with a centrally placed enlarged portion 180, as shown in FIG.3. Another enlarged portion embodiment 180 may have enlarged portions180 on every strut 168, as shown in FIG. 5. Additionally, a proximalself-expanding stent member 160 embodiment may have a firstself-expanding stent member 200 secured to a second self-expanding stentmember 202 where the first self-expanding stent member 200 (or moreproximal stent) may have alternating more distally placed barbs 165along the struts 168 with more proximally placed barbs 165 along thestruts 168, as shown in FIG. 9. Another proximal self-expanding stentmember 160 embodiment may include one or more struts 168 having enlargedportions 180 generally centrally placed along the length of the struts168, followed by alternating more distally placed barbs 165 with moreproximally placed barbs 165 along the struts 168, as shown in FIG. 11.

For some embodiments, the first self-expanding member 200 of theproximal self-expanding stent member 160 may further include a pluralityof barbs 165 having sharp tissue engaging tips that are configured toextend radially outward and distally in a deployed expanded state. Thisconfiguration may be useful in order to engage tissue of an innerluminal surface 132 of a patient's vasculature 130 and mechanicallyanchor the stent graft 150 to the vasculature 130, in addition to theanchoring function provided by the outward radial force of the proximalself-expanding stent member 160 against the inner luminal surface 132 ofthe patient's vasculature 130 when the stent graft 150 is in a deployedstate. The second self-expanding member 202 of the proximalself-expanding stent member 160 may be secured to the proximal end 154of the main body 152 of the stent graft 150 with one or more struts 168and/or connector members 216 mechanically coupled to a proximalconnector ring 164.

When loaded on the delivery catheter 100, the first and secondself-expanding members 200, 202 of the proximal self-expanding stentmember 160 may be radially constrained by releasable belts 104 and 106which may be releasably held in a constraining configuration by arelease member, such as a release wire 120. FIG. 2 shows an embodimentof the proximal self-expanding stent member 160 where the firstself-expanding member 200 is being radially constrained by a firstreleasable belt 104 and the second self-expanding member 202 is beingradially constrained by a second releasable belt 106. The firstreleasable belt 104 may be released by a first release wire 120 and thesecond releasable belt 106 may be deployed by the second release wire120. The first and second self-expanding members 200 and 202 of theproximal anchor member may only be released after the outer sheath 102has been retracted, as shown in FIG. 2, in order to expose the stentgraft 150.

The strut 168 structure of the proximal self-expanding stent member 160and/or distal self-expanding stent member 170 may be formed from acylindrical metal tube structure which is carved or bore by laser orother cutting device. Thereafter, the cut tube may be heat set into twoseparate forms or states such as an expanded state andnon-expanded/contracted state. FIG. 3 shows an example of a non-expandedstate. The proximal self-expanding stent member 160 and/or distalself-expanding stent member 170 may include one or more barbs 165. Abarb 165 may be any outwardly directed protuberance, typicallyterminating in a sharp point that is capable of at least partiallypenetrating a body passageway in which the stent graft 150 is deployed(typically the initial and medial layers of a blood vessel such as theabdominal aorta). The number of barbs 165, the length of each barb 165,each barb 165 angle, and the barb 165 orientation may vary from barb 165to barb 165 within a single anchor member or between multiple anchormembers (i.e., proximal self-expanding stent member 160 and/or distalself-expanding stent member 170) within a single stent graft 150.Although the various barbs 165 (and tuck pads 166, as will be discussedbelow) may be attached to or fixed on the struts 168, it may bepreferred that they are integrally formed as part of the struts 168.When either the proximal self-expanding stent member 160 and/or distalself-expanding stent member 170 is deployed in the abdominal aorta, forexample, typically in a location proximal to the aneurysm and anydiseased tissue, barbs 165 may be designed to work in conjunction withthe distally-oriented blood flow field. In this location, the barbs 165may penetrate the tissue and prevent axial migration of the stent graft150. As such, the barbs 165 may be oriented proximally with respect tothe main body 152 section. However, the number, dimensions,configuration and orientation of barbs 165 may vary significantly, yetbe within the scope of the present invention.

The staged deployment of the proximal self-expanding stent member 160may also facilitate self-alignment of the stent graft 150. For instance,upon deployment of the proximal self-expanding stent member 160, thegraft may be free to expand and enable distal fluid flow to flow throughthe stent graft 150 and create a “windsock” effect. That is, the distalfluid flow may apply a slight distal force generally upon the main body152. This distal force may help to align at least the main body 152 andproximal self-expanding stent member 160 within the patient'svasculature 130, which may be particularly advantageous duringdeployment of the stent graft 150 within the angulated vasculature 130,for example.

In some embodiments of the stent graft 150, one or more struts 168 mayinclude tuck pads 166. Additionally, the one or more struts 168 may havetuck pads 166 positioned such that the tuck pads 166 are generallyaligned with a barb 165 extending from an adjacent strut 168, as shownin FIG. 11. As such, during preparation of the stent graft 150 into itsreduced diameter delivery configuration (or non-expanded/contractedstate), each barb 165 may be placed, for example, behind an adjacentstrut 168 and/or tuck pad 166 in order to prevent the barbs 165 fromradially extending and contacting the inside of a outer sheath 102 ordelivery catheter 100 during delivery of the stent graft 150, as well asto prevent undesired contact of the barbs 165 with the inside luminalsurface 132 of a patient's vasculature 130.

As illustrated in FIG. 3A, the struts 168 may have variouscircumferential dimensions and/or cross sectional areas 169. Enlargedportions 180 of a strut 168 may also include varying radial lengthsgenerally along a longitudinal axis of the strut 168. Enlarged portions180 may be aligned with barbs 165 and/or located at a generally unstableportion of a strut 168. In some stent graft 150 embodiments, when thestent (i.e., proximal self-expanding member 169) is in a compressedstate, enlarged portions 180 may abut each other and may have one ormore flat sides which prevent slippage by each other. Adjacent enlargedportions 180 that abut each other and circumferentially interfere witheach other may be axially coextensive. In a radially compressed state,for example, the one or more enlarged portions 180 may be compressed toa radial diameter that is no greater than the remaining part of thestent 168.

In some embodiments, one or more struts 168 may have a tapered section300. For example, one or more struts 168 may have a tapered section 300in order to evenly distribute strain induced at least when the stent isin a constrained state. The strut 168 may taper from a first end portionof the strut 168 to a smaller transverse cross section towards a middleportion of the strut 168. As shown in FIG. 7B, a strut 168 embodimentmay taper from a proximal end 400 portion towards a respective middleportion 402 and taper to a reduced transverse cross section from adistal end portion 404 towards a respective middle portion 402. Thestrut 168 may taper over half or approximately half of the length of thestrut 168. In addition, the strut 168 may taper generally over theentire length of the strut 168, such as from the apex or crown of theanchor member or stent to the middle of the strut or to the firstdiscontinuity feature (i.e., an enlarged portion 180, barb 165, tuck pad166 and the like). The struts 168 may taper in at least one transversedimension of the strut 168. Additionally, the struts 168 may taper alonga circumferential direction about the longitudinal axis of the struts168 may have a substantially constant thickness in a radial directionrelative to the longitudinal axis of the stent, such as the proximalself-expanding stent member 160. The struts 168 may taper along a radialdirection relative to the longitudinal axis of the anchor member orstent and the struts 168 may have a substantially constant thickness ina circumferential direction about the longitudinal axis of the anchormember or stent. The taper angle of a tapered section 300 of a strut 168may be about 1 degree to about 3 degrees inclusive, about 1.5 degree toabout 2.5 degrees inclusive, or about 1.75 degree to about 2.25 degreesinclusive. The strut 168 embodiments may taper continuously from eachend portion to the respective middle portions, such as is shown by wayof example in FIG. 9. The struts may include a stepped taper embodiment302 which tapers in discrete steps rather than a smooth continuous taperfrom the distal and proximal end portions 404 and 400 of the respectivemiddle portions 402 in either radial direction about the longitudinalaxis. Such an embodiment is shown by way of example in FIG. 7C. Thestruts may also taper in a circumferential direction about thelongitudinal axis, as shown in FIG. 8. The tapered sections 300 of thestruts 168 may extend from proximal and distal end portions 400 and 404of the struts 168 to respective strut structures (i.e., enlargedportions 180) disposed in, for example, the middle portion 402 of therespective strut 168, as shown by way of example in FIG. 8.

FIG. 5 illustrates a portion of a stent 500 embodiment which mayfunction as a proximal self-expanding stent member 160. The stent 500may include a plurality of struts 168 extending axially between theproximal end 402 and distal end 404 thereof. The stent 500 may beoriented in either direction, depending on the application. Both theproximal and distal ends 400 and 404 may have a plurality of crownsadjoining adjacent struts 168. The distal end 404 may have a pluralityof connecting members 216 configured to connect the stent 500 to themain body 152 or other structure. The stent 500 embodiment may havevarious features (i.e., tuck pads 166, etc.) and structures and is notlimited to the strut 168 features and structures illustrated herein. Forexample, the stent 500 may have a body defined by a lattice structure ora helical structure.

Optional taper (or tapers) may be incorporated into one or more of thestruts 168 of the various stent 500 embodiments, as well as the variousconnector members 216. In general, incorporating one or more tapers intoone or more of the struts 168 in one or more stents 500 may providegreater space in the tapered section 300 to accommodate alternativefeatures such as barbs 165 and tuck pads 166. In addition, it may allowfor a smaller deployment profile when the components are in a radiallycollapsed delivery configuration. When configuring the various stents500 into this reduced diameter delivery profile(non-expanded/constrained state), the stents 500 may experience a largedegree of bending strain that may be poorly distributed. Taperingcertain stent 500 struts 168 in particular locations may help todistribute this strain more evenly throughout the stent 500 and/or strut168 which may assist in preventing strain damage to the stent 500.

FIG. 5 illustrates a section of a stent 500, such as a proximalself-expanding stent member 160, in which the struts 168 taper from aproximal end 400 width to a minimum width about the middle portion 402of the strut 168. An example transverse cross-section of the strut 168taken along line 6AA-6AA, which is generally located in the proximal end400 region of a strut 168, of FIG. 5 is shown in FIG. 6AA (which may ormay not equal a width of strut 168 in the apex region or distal end404). Another example transverse cross-section of the strut 168 takenalong line 6A-6A, which is generally located in the minimum width, ornear the middle portion 402 region of the strut 168, of FIG. 5 is shownin FIG. 6A. The optional taper, which may be expressed as the taperratio, is the ratio of the maximum width (as shown, for example, in FIG.6AA) to the minimum width (as shown in FIG. 6A) of a cross sectionalarea 169. The taper ratio may vary widely depending on, for example, theparticular region of the strut 168 or connector member 216, the materialused, and other factors. Taper ratios ranging from about 1 to about 10or greater may be within the scope of the present invention. It may alsobe within the scope of the present invention for the struts 168 to haveno taper (as shown by way of example in FIG. 7A).

FIGS. 6A-6EE, illustrate a variety of examples of varying transversecross-sectional views taken at two different locations along a singlestrut 168. These figures illustrate examples of the different shapes andsizes a single cross sectional area 169 of a strut 168 may have. Forinstance, as described above, FIGS. 6A and 6AA show a pair of transversecross section views of the strut 168 embodiment of FIG. 5 taken alongthe lines 6A-6A and 6AA-6AA which illustrates the rectangular shape ofthe cross sectional area 169 and the change in size of the crosssectional area 169 at two different locations along the strut 168. FIGS.6B and 6BB illustrate another example embodiment of paired transversecross section views of another strut 168 embodiment which illustratesthe trapezoidal shape of the cross sectional area 169 and the change insize of the cross sectional area 169 at two different locations alongthe strut 168. FIGS. 6C and 6CC illustrate another example embodiment ofpaired transverse cross section views of another strut 168 embodimentwhich illustrates the inverse trapezoidal shape of the cross sectionalarea 169 and the change in size of the cross sectional area 169 at twodifferent locations along the strut 168. FIGS. 6D and 6DD illustrateanother example embodiment of paired transverse cross section views ofanother strut 168 embodiment which illustrates the elliptical shape ofthe cross sectional area 169 and the change in size of the crosssectional area 169 at two different locations along the strut 168. FIGS.6E and 6EE illustrate another example embodiment of paired transversecross section views of another strut 168 embodiment which illustratesthe circular shape of the cross sectional area 169 and the change insize of the cross sectional area 169 at two different locations alongthe strut 168. The transverse cross sectional area 169 of one or morelocations along a strut 168 are not limited to the sizes and shapesdisclosed herein, and may be any number of sizes and shapes that may beincorporated in a strut 168 and/or stent 500 configuration.

A proximal self-expanding stent member 160 may have, for example, one ormore struts 168 having a proximal end 400 portion and/or distal end 404portion which may be made from NiTi and an effective maximum strut 168width ranging from about 0.016 to about 0.032 inch; particularly fromabout 0.022 inch and about 0.028 inch, and a minimum strut 168 widthbetween about 0.010 inch and about 0.026 inch; particularly from about0.012 inch and about 0.022 inch. Additional tapered strut 168embodiments are described and shown herein in the figures which may beused in other anchor members (such as the proximal and distalself-expanding stent members 160 and 170), stent 500 embodiments orconnector members 216 described herein, and may be incorporated in anynumber of components and made from any number of materials. For example,tapering of the struts 168 in any configuration described herein mayimprove the strain distribution at least between the proximal end 400portions and distal end 404 portions of the struts 168.

Various types of taper features or configurations may be implemented inany number of struts 168 for achieving a variety of strut 168characteristics. For example, one or more struts 168 may include a taperhaving an offset radii and/or combinations of elliptical and/or circularapex radii in order to further cause the desired behavior duringassembly into a reduced-diameter delivery configuration as well aseffective delivery and performance in vivo. For example, the proximalend 400 portion, or apex, width may be the minimum width of the strut168 which untapers towards the middle portion 402 of the strut 168,which may have the maximum width of the strut 168. The tapering from theproximal end 400 portion to the middle portion 402 of the strut 168 maybe continuous, stepped in discrete steps 410 with straight untaperedportions between each discrete step (as shown by way of example in FIGS.7C and 8) or a combination thereof. Furthermore, untapering of the strut168 may be in the radial and/or circumferential direction along thelongitudinal length of the strut 168.

The strut 168 may include an enlarged portion 180 located in about themiddle portion 402 of one or more of the struts 168, as shown by way ofexample in FIG. 5. By way of further example, one or more enlargedportions 180 may be located along every other strut 168 of the stent500. The one or more enlarged portion 180 may be located along a strut168 in various locations, such as near or at the proximal end 400portion, middle portion 402, and/or distal end 404 portion of the strut168. Additionally, the one or more enlarged portions 180 may be locatedat offset locations relative to enlarged portions 180 (or otherfeatures) along neighboring struts 168.

In some cases, the one or more enlarged longitudinal sections orenlarged portions 180 may have an enlarged transverse dimension that isabout 1.5 times to about 3 times the nominal transverse dimension of thestrut 168 in a direction of the enlargement. Additionally, the enlargedportions 180 may have an undulating configuration of the nominal strut168. Furthermore, the enlarged portion 180 may have an oval enlargementof the nominal strut. Each strut 168 of the stent 500 having an enlargedportion 168 along the length of the strut 168 may have only one enlargedportion 180. Alternatively, each strut 168 of the stent 500 having anenlarged portion 180 along the length of the strut 168 may have morethan one enlarged portion 180. The enlarged portions 180 are not limitedto what are described and shown herein, and may be sized, featured,shaped, and proportioned in any number of ways that may assist inassembly or use of the stent 500. Additionally, any number of materialsmay be used and may vary between struts 168, anchor members (such as theproximal and distal self-expanding strut members 160 and 170), and/orstents 500.

FIG. 10A shows an example portion of a cylindrical stent embodiment 500in a constrained configuration including struts 168 having generallycoaxially aligned enlarged portion 180 embodiments having circular oroval features. FIG. 10B shows an example portion of a cylindrical stentembodiment 500 in a constrained configuration having struts 168 withgenerally coaxially aligned enlarged portion 180 embodiments havingsquare or rectangular features. FIG. 10C shows a portion of acylindrical stent embodiment 500 in a constrained configurationincluding struts 168 having undulating deflected portions 182 which maybe configured to physically separate adjacent struts 168 in acircumferential direction.

One or more struts 168 of a stent embodiment 500 may have a steppedtaper 302 feature generally along the length of the strut 168. Forexample, one or more struts 168 may have a stepped taper 302 from theproximal end 400 to the respective middle portion 402 of the strut 168and/or a stepped taper 302 from the distal end 404 to the middle portion402 of the strut 168, wherein the stepped taper 302 may be in eitherradial direction about the longitudinal axis of the strut 168, as shownby way of example in FIG. 7C, or the circumferential direction about thelongitudinal axis, as shown by way of example in FIG. 8. The tapercharacteristics of a strut 168 may be continuous, stepped or any othershape configured to evenly distribute strain induced by the constraintof the constrained non-expanded stent 500.

FIG. 7A illustrates an example longitudinal section view taken alongline 7A-7A of the strut 168 in FIG. 5 which shows a generallyrectangular cross sectional area 169 having no radial tapering about thelongitudinal axis. FIG. 7B illustrates another example of a longitudinalsection view of a strut 168 which shows a generally tapered crosssectional area 169 due to radial tapering about the longitudinal axis ofthe strut 168. In FIG. 7B, the strut 168 tapers continuously from eachend portion (the proximal and distal ends 400 and 404) to the middleportion 402 such that the middle portion 402 generally has the minimumstrut 168 width in the radial direction. FIG. 7C shows another examplestrut 168 embodiment in longitudinal section including a radial steppedtapering 302 about the longitudinal axis of the strut 168. In FIG. 7C,the strut 168 generally tapers in steps continuously from each endportion (the proximal and distal ends 400 and 404) to the middle portion402 such that the middle portion 402 generally has the minimum strut 168width in the radial direction.

FIG. 8 shows a portion of an embodiment of a stent 500 including struts168 having a circumferential stepped taper 302 configuration about thelongitudinal axis of the strut 168. The middle portion 402 of each strut168 may also include an enlarged portion 180 extending, for example, ina circumferential direction. Portions of the stepped taper 302 of astrut 168 that may be directly adjacent an enlarged portion 180 may havethe minimum strut 168 width in the circumferential direction. However,any number of combinations of tapering in any direction may be used.

FIG. 9 shows a stent embodiment 500 where the proximal self-expandingstent member 160 has a first self-expanding member 200 secured to asecond self-expanding member 202 where the first self-expanding member200 has alternating more proximally placed barbs 165 along the struts168 with more distally placed barbs 165 along the struts 168. Inaddition, the stent embodiment 500 may have a continuous taper in thesecond self-expanding member 202, which is the portion of the proximalself-expanding stent member 160 adjacent the main body 152. Each strut168 on the first self-expanding member 168 may have a barb 165 in adifferent location relative to a neighboring strut 168. The barbs 165may be formed integrally with the struts 168, but may otherwise bemanufactured, for example, as a separate component attached to thestruts 168. In general, the struts 168 and the barbs 165 of the stentembodiments 500 and anchor members may be self-expanding, that is, uponrelease of a constraining force, the struts 168 may move radially apartand the barbs 165 may extend radially outward. Other configurations,such as balloon expansion, are also contemplated within the presentinvention.

In addition, stent embodiments 500 may include struts 168 including tuckpads 166, which may be positioned along a strut 168 such that the tuckpads 166 are axially aligned with a barb 165 positioned on a neighboringstrut 168. Similar to the barbs 165 and enlarged portions 180, thenumber, dimensions, configurations and orientations of the tuck pads 166may vary between struts 168, stent embodiments 500 and anchor members(such as the proximal and distal self-expanding stent members 160 and170 described herein).

During preparation of a stent graft embodiment 150 (and therefore one ormore proximal self-expanding stent members 160) into a reduced diameterdelivery configuration, one or more barbs 165 may be placed behind acorresponding strut 168 and/or tuck pad 166, if present, in order toprevent the barbs 165 from contacting the inside of a outer sheath 102or delivery catheter 100 during delivery of the stent graft 150 and fromundesired contact with the interior luminal surface 132 of the patient'svasculature 130. As described in copending U.S. patent application Ser.No. 09/917,371 to Chobotov et al., now U.S. Pat. No. 6,761,733, andwhich is incorporated by reference herein in its entirety, a releasebelt may be disposed in one or more grooves (not shown) disposed on oneor more struts 168 which may assist in retaining the proximalself-expanding stent member 160 in the reduced diameter deliveryconfiguration.

For example, upon deployment of stent graft 150, and more particularlythe proximal self-expanding stent member 160, (typically accomplished,at least in part, by release of one or more belts, such as the proximalreleasable belts 104 and 106), the radial expansion of the proximalself-expanding stent member 160 results in a displacement of struts 168so that the distance between them increases. Eventually, thedisplacement between the struts 168 become large enough to enable thebarbs 165 to be released from behind the adjacent strut 168 and/or tuckpad 166 and engage the interior luminal surface 132 of the patient'svasculature 130. In general, the barbs 165 may release into a positionsuitable for engaging the interior luminal surface 132 of a patient'svasculature with a time constant that is generally an order of magnitudelower than the time constant associated with the radial expansion of thestent 500 embodiment or anchor member (such as the proximalself-expanding stent member 160). In other words, during the stent 500or anchor member deployment process, the one or more barbs 165 maycomplete their deployment before the stent 500 or anchor member is fullyexpanded so that the barbs 165 may engage the interior luminal surface132 of the vasculature 130 with maximum effectiveness.

Referring again to FIG. 9, the proximal self-expanding stent member 160may include struts 168, any one of which may further comprise one ormore barbs 165. In addition, optional tuck pads 166 may be positionedalong a strut 168 such that the tuck pad 166 is coaxially aligned with abarb 165 on a neighboring strut 168 in order to shield the neighboringbarb 165 at least when the stent graft 150 is in its reduced diameterdelivery configuration. Struts 168 and/or tuck pads 166 may also includea tuck slot 167 which may assist in retaining a barb 165 while the stentgraft 150 (and consequently the proximal self-expanding stent member160) is in its reduced diameter delivery configuration. Upon deploymentof a stent graft 150 embodiment, the one or more barbs 165 may bereleased from respective tuck slots 167 and thereafter placed in anoperational or deployed configuration for engaging a patient'svasculature 130.

FIG. 11 shows a portion of a cylindrical stent embodiment 500 in agenerally constrained and flattened configuration having struts 168 witha coaxial enlarged portion 180 embodiments and undulating deflectedportions 182. The undulating deflected portions 182 may have barbs 165positioned at offset proximal and distal locations along neighboringstruts 168 which may aid in efficiently compacting the struts 168 andbarbs 165 in a constrained configuration for delivery into a patient'sbody. By alternating axial location of the barbs 165 and/or enlargedportions 180 along neighboring struts 168, the stent 500 may beoptimally compressed. The undulating deflected portions 182 of a strut168 may enable multiple lateral contact points within the stent 500.Such multiple contact points may aid in restraining or compacting thestent 500 in a constrained/non-expanded state. In some embodiments, oneor more struts 168 may have enlarged longitudinal sections or enlargedportions 180 that may be disposed in a substantially longitudinalorientation between the proximal end and distal end of the stent 500when the stent 500 is in the constrained state. Additionally, the one ormore struts 168 may be disposed in an undulating pattern. FIG. 12 showsa transverse cross section view of the stent 500 portion of FIG. 11taken along lines 12-12 of FIG. 11. FIG. 12 illustrates an example ofthe varying circumferential cross sectional areas 169 of the struts 168taken along a transverse cross section of the strut 500.

As discussed above, some embodiments of a modular endovascular stentgraft assembly may include a bifurcated graft member 600 with a proximalstent or anchor member 602 secured thereto. In some cases, the main bodymember 604 may be formed from a supple graft material, such as ePTFE,having a main fluid flow lumen 606 therein. FIG. 13 illustrates such anembodiment. Referring to this figure, the main graft portion 604 mayinclude an ipsilateral leg 608 with an ipsilateral fluid flow lumen 610in communication with the main fluid flow lumen 606, a contralateral leg612 with a contralateral fluid flow lumen 614 in communication with themain fluid flow lumen 606 and a network of inflatable channels 616disposed on the main graft member 604. For some embodiments, the maingraft or main body member 604 may have an axial length of about 5 cm toabout 10 cm, more specifically, about 6 cm to about 8 cm in order tospan an aneurysm 622 of a patient's aorta 618 without engaging thepatient's iliac arteries 620 directly with the legs 608 and 612 of themain graft member 604 (see FIG. 14).

The inflatable channels of the network of inflatable channels 616 may bedisposed on any portion of the main graft or main body member 604including the ipsilateral and contralateral legs 608 and 612. Thenetwork of inflatable channels 616 may be configured to accept ahardenable fill material to provide structural rigidity to the main body604 member when the network of inflatable channels 616 are in aninflated state and the inflation material has been cured or hardened.Radiopaque inflation material may be used to facilitate monitoring ofthe fill process and subsequent engagement of graft extensions. Thenetwork of inflatable channels 616 may also include at least oneinflatable cuff 624 disposed on a proximal portion of the main bodymember which may be configured to seal against an inside surface of apatient's vessel, such as the aorta.

The proximal anchor member 626, which may have a substantially tubularor cylindrical configuration, may be disposed at a proximal end 628 ofthe main body member 604 and secured to the main body member 604 in anysuitable manner including stitching, adhesive bonding, welding, and thelike. The proximal anchor member 626 may also be secured to the mainbody 604 with a resilient connector ring (not shown) which may beembedded in a proximal end or portion 628 the main body 604. Theproximal anchor member 626 may have a self-expanding proximal stentportion 630 secured to a self-expanding distal stent portion 632. Eachof these stent portions 630 and 632 may include an undulating elongatestent element that may be disposed in a somewhat serpentine orsinusoidal configuration, as shown above with regard to stent members160 and 170. Each of the stent portions 630 and 632 of the proximalanchor member 626 of the stent graft 600 in FIG. 13 may share any or allof the features, dimensions or materials of stent members 160 and 170discussed above. For example, the proximal and distal stent portions 630and 632 of the proximal anchor member 626 may include tapered struts 634that extend between crown portions 636 of each respective stent portion630 or 632. Such tapered struts 634 may have any or all of the features,dimensions, and materials of the struts discussed above and include atapered strut configuration that allows for the strain imposed on thestrut structure to be evenly distributed through the structure of thestent portion or portions 630 and 632.

In some cases, the proximal stent portion 630 may be secured to thedistal stent portion 632 with one or more struts or strut segments 638disposed between the respective proximal and distal stent sections 630and 632. Some embodiments of such interconnecting struts 638 may have across sectional area that is substantially the same as or greater than across sectional area of proximal stent portions 630 or distal stentportions 632 adjacent the strut 638. Such configurations may be usefulin avoiding points of concentrated stress in the proximal anchor member602 or struts 638 which couple components thereof. For some embodiments,the proximal stent portion 630 of the proximal anchor member 602 mayfurther include a plurality of barbs 640 having sharp tissue engagingtips 642 that are configured to extend in a radial outward direction ina deployed expanded state (see FIG. 15). For some embodiments, eachstent portion 630 and 632 of the proximal anchor member 602 may includeabout 5 crowns 636 to about 8 crowns 636 at either end of the respectivesection 630 or 632 and may be made from a superelastic alloy such assuperelastic NiTi alloy.

At least one tubular ipsilateral graft extension 644 having a fluid flowlumen 646 disposed therein may be deployed with the fluid flow lumen 646of the graft extension 644 sealed to and in fluid communication with thefluid flow lumen 610 of the ipsilateral leg 608 of the main body member604. In addition, at least one tubular contralateral graft extension 648having a fluid flow lumen 650 disposed therein may be deployed with thefluid flow lumen 650 of the graft extension 648 sealed to and in fluidcommunication with the fluid flow lumen 614 of the contralateral leg 612of the main body member 604. For some embodiments, the graft extensions644 and 648 may include an interposed self-expanding stent 652 disposedbetween at least one outer layer and at least one inner layer of supplelayers of graft material. The interposed stent disposed between theouter layer and inner layer of graft material may be formed from anelongate resilient element helically wound with a plurality oflongitudinally spaced turns into an open tubular configuration. For someembodiments, the interposed stent 652 may include a superelastic alloysuch as superelastic NiTi alloy. In addition, the graft material of eachgraft extension 644 and 648 may further include at least one axial zoneof low permeability for some embodiments.

For some embodiments, an outside surface of the graft extension 648 maybe sealed to an inside surface of the contralateral leg 612 of the mainbody 604 when the graft extension 648 is in a deployed state. For someembodiments, the axial length of the ipsilateral and contralateral legs608 and 612 may be sufficient to provide adequate surface area contactwith outer surfaces of graft extensions 644 and 648 to providesufficient friction to hold the graft extensions 644 and 648 in place.For some embodiments, the ipsilateral and contralateral legs 608 and 612may have an axial length of at least about 2 cm. For some embodiments,the ipsilateral and contralateral legs 608 and 612 may have an axiallength of about 2 cm to about 6 cm, more specifically, about 3 cm toabout 5 cm.

For the bifurcated stent graft embodiment 600 discussed above or anyother suitable stent graft embodiment discussed herein that includes aproximal self-expanding anchor member 602, it may be desirable in somecases to constrain each of the proximal and distal stent portions 630and 632 separately so that each of the proximal and distal stentportions 630 and 632 of the proximal anchor member 602 can be deployedfrom a radially constrained state independent of each other. FIG. 14shows the stent graft 600 having an 8 crown distal stent portion 632with marker elements 654 disposed at a distal end 656 of the distalstent portion 632. Other than this variation in the proximal anchorconfiguration, the stent graft of FIG. 14 may have the same features,dimensions and materials as those of the stent graft 600 shown in FIG.13.

The stent graft 600 of FIG. 14 is shown in a partially deployed statewithin an abdominal aorta 618 of a patient with the proximal end 628 ofthe main body 604 disposed just below and in a non-interferingrelationship with the renal arteries 658 which extend from and are incommunication with the patient's aorta. The main body 604 of the stentgraft 600 also extends substantially across the aneurysm 622 of theaorta 618, however, this relationship may vary depending on the size ofthe graft 600 used and the morphology of the aneurysm 632. The proximalstent portion 630 of the proximal anchor member 602 is still constrainedby a releasable member or belt 660 such that it has an outer dimensionor profile suitable for delivery within a catheter assembly within thepatient's vasculature. The distal stent portion 632, however, has beenreleased from a constrained state and has expanded radially such thatthe distal end 656 of the distal stent portion 632 has expandedoutwardly in approximation to the inner surface 662 of the patient'saorta 618.

In such cases, a proximal anchor member 602 configured to allow thedistal end 656 of the distal stent portion 632 to so expand may bedesirable. For example, the markers 654 disposed at the distal end 656of the distal stent portion 632 are substantially open and are close toor in contact with the inner wall 662 of the patient's aorta 68providing good visualization of the position of the partially deployedstent graft 600 under fluoroscopy. This configuration may allow thephysician deploying the stent graft 600 to visualize the position of thestent graft 600 and accurately predict what the final position of thestent graft 600 will be after complete deployment. However, such aconfiguration may also allow the physician to adjust the position of thestent graft 600 prior to full deployment of the proximal anchor member602. In other words, the stent graft 600 and markers 654 at the distalend 656 of the distal stent portion 632 are sufficiently expanded sothat the physician can easily see how the stent graft 600 will bepositioned when fully deployed before the physician has deployed theproximal stent portion 630 in which case the barbs 640 or other tissueengaging members of the proximal stent portion 630 engage the tissue ofthe inner wall 662 of the patient's aorta 618.

We have found that in some instances, in order to configure an anchormember 602 such that the distal end 656 of the distal stent portion 632opens or radially expands sufficiently upon release from a constrainedstate, that certain design parameters or criteria may be desirable. Inparticular, such a stent portion 632 may benefit from a configurationthat produces a good distal opening force or maximum opening force in anoutward radial direction. In order to produce a generous opening forcein an outward radial direction, the section of the struts 634 and crowns636 of the proximal and distal stent portions 630 and 632 may beincreased, however, it may also be desirable to adjust the taperingprofile of the struts 634 in order to maintain a substantially evendistribution of strain throughout the structure of the stent portions630 and 632. For some embodiments, a useful outward opening force mayinclude about 0.5 to about 0.75 lbf of force for a stent embodiment thatis about 14 mm to about 16 mm in outer diameter in a relaxedunconstrained state.

In cases such as the stent graft embodiment 600 of FIG. 13 wherein theproximal anchor member 602 includes both a proximal stent portion 630and a distal stent portion 632, it may be useful to vary the axiallengths of the respective proximal and distal portions 630 and 632 ofthe anchor member 602. Such an unsymmetric arrangement may be beneficialin cases such as the partial deployment sequence step shown in FIG. 14wherein the constraint on the distal stent portion 632 has been releasedso as to allow radial expansion of the distal portion 632 but theproximal stent portion 630 remains constrained.

FIG. 15 illustrates an embodiment of the proximal anchor member 602having a 5 crown proximal stent portion 630 and a five crown distalstent portion 632. An attachment ring 664 is secured to each crown 636of the distal end 656 of the distal stent portion 632. Such attachmentrings 664 may be secured to the proximal end 628 of main body 604 bystitching the ring 664 to the flexible material of the main body portion604 with suture or any other suitable material. Such attachment rings664 may also be secured to the main body 604 by any other suitablemethod including any of the attachment methods and devices discussedabove. A cutaway portion 668 of the proximal anchor member 602 is shownat the ends of arrows 665 to illustrate an element of the proximalanchor member 602 for further discussion. The cutaway portion 668includes a distal crown 670 and respective stent struts 634 attachedthereto from the distal stent portion 632 and a proximal crown 672 andrespective stent struts 634 attached thereto from the proximal stentportion 630. The proximal end of the distal stent portion 632 is securedto the distal end 676 of the proximal stent portion 630 by strutsegments 638.

FIG. 16 illustrates the cutaway portion 668 of the proximal anchormember 602 of FIG. 15 with an adjacent arrow 678 that indicates theaxial length of the proximal stent portion 630 and an arrow 680 thatindicates the axial length of the proximal stent portion 630 togetherwith the distal stent portion 632 or, in other words, the axial lengthof the proximal anchor member 602 as a whole. For some embodiments, ithas been determined that one or more of the design parameters discussedabove may be optimized by use of a proximal anchor member 602 having aproximal stent portion 630 and a distal stent portion 632 wherein theaxial length of the proximal anchor member 602 as a whole (L_(stent),divided by the axial length of the proximal stent portion 630(L_(proximal)) is a ratio of about 1.75 to about 2.5, more specifically,about 1.75 to about 2.1, and even more specifically, about 1.75 to about1.9. Such a configuration may be useful for a multi-element stent orproximal anchor member 602 in order to maximize opening force andminimize peak strain within the proximal anchor member 602.

It has also been discovered that for such proximal anchor memberembodiments 600 as shown in FIG. 16 including unsymmetric axial lengthsof the proximal stent portion 630 and distal stent portion 632, that itmay also be useful to include unsymmetric taper lengths. FIG. 17illustrates the cutaway portion 668 of the proximal anchor member 602 ofFIG. 15 with an arrow 682 that indicates the axial length of the taperedportion 684 of the strut 634 that tapers from the proximal end 674 ofthe distal stent portion 632 towards the distal end 656 of the distalstent portion 632. Such a tapered portion 684 extends from the crown 686of the distal stent portion 632 at a proximal end thereof to an axialposition of minimum strut cross section 688 between the proximal crown686 and distal crown 670 of the distal stent portion 632. Distal of theposition of minimum section 688 on the strut 634, the strut 634 maybegin to flare and increase in section towards the distal crown 670.Thus, the point of minimum section 688 on the strut 634 represents theendpoint of the tapered portions 684 of the strut 634 which begin ateach respective crown 670 and 686 of the distal stent portion 632. Forsome stent embodiments 602, a strut taper configuration wherein theaxial length of the proximal anchor member as a whole 602 or L_(stent)divided by the axial length of the tapered strut 634 from the crown 686of the distal stent portion 632 at a proximal end 674 thereof to anaxial position of minimum strut cross section 688 between the proximalcrown 686 and distal crown 670 of the distal stent portion 632(L_(taper)) is about 3.0 to about 4.5, may be particularly useful inorder to maximize opening force and reduce or minimize peak strainswithin the structure of the proximal anchor member 602. It should alsobe noted that such unsymmetric taper lengths may also be used formulti-element stents or proximal anchor members 602 having stentportions 630 and 632 of equal axial length.

Another design parameter that may be useful when maximizing openingforce and minimizing peak strain within a proximal anchor member 602 isselection of the inner crown radius of the crowns 636 at each end of therespective proximal and distal stent portions 630 and 632. FIGS. 18 and19 illustrate an inner crown radius R of a distal crown 670 of thedistal stent portion 632 of the proximal anchor member 602. For someembodiments, it may be useful to have an inner crown radius R of about0.001 inches to about 0.005 inches, more specifically, about 0.001inches to about 0.004 inches. It should be noted that such inner crownradii dimensions R may also be used for single element stents orproximal anchor members 160 and 170, particularly in embodiments whereit is desirable to maximize opening force and minimize peak strainswithin the proximal anchor member.

For some particular stent graft embodiments 600 having a bifurcated mainbody 604 and a multi-element proximal anchor member 602, the proximalanchor member 602 may be configured to open to a maximum diameter ofabout 29 mm to about 31 mm, more specifically, about 30 mm, the proximalanchor member may have an overall axial length L_(stent) Of about 35 mmto about 37 mm, more specifically, about 36 mm, an opening force ofabout 0.5 lbf to about 0.7 lbf, more specifically, about 0.6 lbf, and aratio of the axial length 680 of the anchor member 602 L_(stent) dividedby the axial length 678 of the proximal stent portion 630 L_(proximal)of about 2.0 to about 2.2, more specifically, about 2.1. Such anembodiment 600 may also have a distal stent portion 632 with a struttaper configuration wherein the length 680 of the proximal anchor member602 as a whole L_(stent) divided by the length 682 of the tapered strut639 from the crown 686 of the distal stent portion 632 at a proximal endthereof to an axial position of minimum strut cross section 688 betweenthe proximal crown 686 and distal crown 670 of the distal stent portion632 (L_(taper)) is about 3.0 to about 3.2, more specifically, about 3.1.Many other embodiments following the design parameters discussed abovemay also be used in order to maximize opening force and minimize peakstrain within the proximal anchor member 602. As discussed above, thesedesign parameters may also be used singly or in any combination in orderto achieve the desired results in either single element stents 160 and170 or multi-element stents 600 having a proximal stent portion 630,distal stent portion 632 or any other number of stent portions.

While preferred embodiments of the invention have been shown anddescribed herein, it will be understood that such embodiments areprovided by way of example only. Numerous variations, changes andsubstitutions will occur to those skilled in the art without departingfrom the spirit of the invention. Accordingly, it is intended that theappended claims cover all such variations as fall within the spirit andscope of the invention.

The number of barbs, enlarged portions or tapers per strut, the lengthof each barb, enlarged portions or tapers, each of the barb angles ortapered angle described above, and the barb, enlarged portion or taperedorientation may vary from barb to barb, enlarged portion to enlargedportion, strut to strut within a single stent or between multiple stentswithin a single graft.

The entirety of each patent, patent application, publication anddocument referenced herein hereby is incorporated by reference. Citationof the above patents, patent applications, publications and documents isnot an admission that any of the foregoing is pertinent prior art, nordoes it constitute any admission as to the contents or date of thesepublications or documents.

Modifications may be made to the foregoing without departing from thebasic aspects of the invention. Although embodiments of the inventionhave been described in substantial detail with reference to one or morespecific embodiments, those of ordinary skill in the art will recognizethat changes may be made to the embodiments specifically disclosed inthis application, yet these modifications and improvements are withinthe scope and spirit of the invention.

Embodiments illustratively described herein suitably may be practiced inthe absence of any element(s) not specifically disclosed herein. Thus,for example, in each instance herein any of the terms “comprising,”“consisting essentially of,” and “consisting of” may be replaced witheither of the other two terms. The terms and expressions which have beenemployed are used as terms of description and not of limitation and useof such terms and expressions do not exclude any equivalents of thefeatures shown and described or portions thereof and variousmodifications are possible within the scope of the invention claimed.The term “a” or “an” can refer to one of or a plurality of the elementsit modifies (e.g., “a reagent” can mean one or more reagents) unless itis contextually clear either one of the elements or more than one of theelements is described. Thus, it should be understood that althoughembodiments have been specifically disclosed by representativeembodiments and optional features, modification and variation of theconcepts herein disclosed may be resorted to by those skilled in theart, and such modifications and variations are considered within thescope of this invention.

Certain embodiments of the invention are set forth in the claim(s) thatfollow(s).

What is claimed is:
 1. A self-expanding cylindrical stent which has aconstrained state and a relaxed expanded state, comprising: alongitudinal axis; at least one tapered strut comprising: a proximalcrown including a proximal end portion comprising a first dimension; adistal crown including a distal end portion comprising a seconddimension, the distal end portion positioned opposite the proximal endportion; and a middle portion positioned approximately halfway betweenthe proximal end portion and the distal end portion, the middle portionextending between and connecting the proximal end portion with thedistal end portion, the middle portion comprising a third dimension thatis smaller than the first dimension and the second dimension, whereinthe at least one tapered strut tapers continuously from the proximal endportion to the middle portion, and from the distal end portion to themiddle portion; a proximal end; a distal end; and a plurality ofresilient struts comprising the at least one tapered strut, theplurality of resilient struts configured to exert an outward radialforce when in the constrained state resulting from confinement of thestent inside an outer sheath, with two or more of the plurality ofresilient struts that are non-adjacent to each other having an enlargedportion which is configured to stabilize the plurality of resilientstruts while the stent is in the constrained state, and at least oneresilient strut of the plurality of resilient struts is absent theenlarged portion and interposed between the non-adjacent resilientstruts having the enlarged portion, the at least one resilient strutabsent the enlarged portion comprises a first resilient strut absent theenlarged portion and a second resilient strut absent the enlargedportion, each comprising one or more barbs extending away from theenlarged portion of one of the two or more of the plurality of resilientstruts that is adjacent to both the first and second resilient strutsabsent the enlarged portion, the enlarged portion comprising: alongitudinal section which is curved and enlarged in a circumferentialorientation relative to the longitudinal axis of the self-expandingcylindrical stent forming an oval shape, and flat sides which are flatalong a radial direction from an inside surface to an outside surface ofthe stent and wherein the flat sides of the enlarged portions abut andcircumferentially interfere with each other with the self-expandingcylindrical stent in the constrained state.
 2. The stent of claim 1wherein the plurality of resilient struts that include with the enlargedportion comprising the longitudinal section which is enlarged in thecircumferential orientation relative to the longitudinal axis of thestent and which is configured to stabilize the at least one strutrelative to the position of the plurality of resilient struts while thestent is in the constrained state.
 3. The stent of claim 2 wherein theenlarged portions of the plurality of resilient struts are enlarged inone transverse dimension of the plurality of resilient struts.
 4. Thestent of claim 3 wherein the enlarged portions are enlarged along acircumferential direction about the longitudinal axis of the stent andthe plurality of resilient struts have a substantially constantthickness in a radial direction relative to the longitudinal axis of thestent.
 5. The stent of claim 1 wherein the enlarged portions have anenlarged transverse dimension that is about 1.5 times to about 3 times anominal transverse dimension of the plurality of resilient struts in adirection of the enlarged portions.
 6. The stent of claim 5 wherein theenlarged portions comprise an undulating configuration of the nominalstrut.
 7. The stent of claim 1 wherein one or more of the plurality ofresilient struts of the stent that comprise the enlarged portioncomprise a plurality of enlarged portions.
 8. The stent of claim 1,wherein the plurality of resilient struts having the enlarged portionsare disposed in a substantially longitudinal orientation between theproximal end and distal end of the stent when the stent is in theconstrained state.
 9. The stent of claim 1 wherein the plurality ofresilient struts are disposed in an undulating pattern.
 10. The stent ofclaim 1 wherein the plurality of resilient struts comprise asuperelastic alloy.
 11. The self-expanding cylindrical stent of claim 1wherein abutting flat sides of the enlarged portions are perpendicularto the longitudinal axis and parallel to each other so as to preventslippage by each other.
 12. The stent of claim 1, wherein some of theplurality of resilient struts have barbs; wherein two or more of theplurality of resilient struts that are non-adjacent to each having theenlarged portion are absent any barbs.
 13. The stent of claim 1, whereinthe enlarged portion is spaced apart from the one or more barbs in anaxial direction and is misaligned in the axial direction.
 14. The stentof claim 1, wherein the first dimension and the second dimension aresubstantially the same.
 15. The stent of claim 1, wherein the firstdimension and the second dimension are different.
 16. The stent of claim1, further comprising a proximal intermediate portion positioned betweenthe proximal end portion and the middle portion, the proximalintermediate portion comprising a fourth dimension that is greater thanthe third dimension and smaller than the first dimension.
 17. The stentof claim 16, further comprising a distal intermediate portion positionedbetween the proximal end portion and the middle portion, the proximalintermediate portion comprising a fifth dimension that is greater thanthe third dimension and smaller than the second dimension.
 18. Anendovascular stent graft, comprising: a main body portion including atleast one tubular portion made from at least one layer of flexiblematerial; and a self-expanding cylindrical stent which has a constrainedstate resulting from confinement of the stent inside an outer sheath anda relaxed expanded state, comprising: a longitudinal axis; at least onetapered strut comprising: a proximal crown including a proximal endportion comprising a first dimension; a distal crown including a distalend portion comprising a second dimension, the distal end portionpositioned opposite the proximal end portion; and a middle portionpositioned approximately halfway between the proximal end portion andthe distal end portion, the middle portion extending between andconnecting the proximal end portion with the distal end portion, themiddle portion comprising a third dimension that is smaller than thefirst dimension and the second dimension, wherein the at least onetapered strut tapers continuously from the proximal end portion to themiddle portion, and from the distal end portion to the middle portion; aproximal end; a distal end; and a plurality of resilient strutscomprising the at least one tapered strut, the plurality of resilientstruts configured to exert an outward radial force when in theconstrained state, with two or more of the plurality of resilient strutsthat are non-adjacent to each other including an enlarged portion whichis configured to stabilize the plurality of resilient struts while thestent is in the constrained state, and at least one resilient strut ofthe plurality of resilient struts is absent the enlarged portion andinterposed between the non-adjacent resilient struts having the enlargedportion, the at least one resilient strut absent the enlarged portioncomprises a first resilient strut absent the enlarged portion and asecond resilient strut absent the enlarged portion that each comprisesone or more barbs extending away from the enlarged portion of one of thetwo or more of the plurality of resilient struts that is adjacent toboth the first and second resilient struts absent the enlarged portion,the enlarged portion comprising: a longitudinal section which is curvedand enlarged in a circumferential orientation relative to thelongitudinal axis of the self-expanding cylindrical stent forming anoval shape, and flat sides which are flat along a radial direction froman inside surface to an outside surface of the stent and wherein theflat sides of the enlarged portions abut and circumferentially interferewith each other with the self-expanding cylindrical stent in theconstrained state.
 19. The endovascular stent graft of claim 18 whereinabutting flat sides of the enlarged portions are perpendicular to thelongitudinal axis and parallel to each other so as to prevent slippageby each other.
 20. A method of loading a delivery catheter with a stentgraft, comprising: providing an endovascular stent graft, comprising: amain body portion including at least one tubular portion made from atleast one layer of flexible material, and a self-expanding cylindricalstent which has a constrained state resulting from confinement of thestent inside an outer sheath and a relaxed expanded state, including: alongitudinal axis, a proximal end, a distal end, and at least onetapered strut comprising a proximal crown including a proximal endportion comprising a first dimension, a distal crown including a distalend portion comprising a second dimension, the distal end portionpositioned opposite the proximal end portion, and a middle portionpositioned approximately halfway between the proximal end portion andthe distal end portion, the middle portion extending between andconnecting the proximal end portion with the distal end portion, themiddle portion comprising a third dimension that is smaller than thefirst dimension and the second dimension, wherein the at least onetapered strut tapers continuously from the proximal end portion to themiddle portion, and from the distal end portion to the middle portion; aplurality of resilient struts comprising the at least one tapered strut,the plurality of resilient struts configured to exert an outward radialforce in the constrained state, with two or more of the plurality ofresilient struts that are non-adjacent to each other including anenlarged portion which is configured to separate and stabilize theplurality of resilient struts while the stent is in the constrainedstate, and at least one resilient strut of the plurality of resilientstruts is absent the enlarged portion and interposed between thenon-adjacent resilient struts having the enlarged portion, the at leastone resilient strut absent the enlarged portion comprises a firstresilient strut absent the enlarged portion and a second resilient strutabsent the enlarged portion that each comprises one or more barbsextending away from the enlarged portion of one of the two or more ofthe plurality of resilient struts that is adjacent to both the first andsecond resilient struts absent the enlarged portion, the enlargedportion comprising: a longitudinal section which is curved and enlargedin a circumferential orientation relative to the longitudinal axis ofthe stent forming an oval shape; and flat sides which are flat along aradial direction from an inside surface to an outside surface of thestent and wherein the flat sides of the enlarged portions abut andcircumferentially interfere with each other with the self expandingcylindrical stent in the constrained state; constraining theself-expanding cylindrical stent of the stent graft about a bushing of adelivery system such that the enlarged portions of the plurality ofresilient struts stabilize the position of the plurality of resilientstruts in the constrained state; and releasably securing theself-expanding cylindrical stent in a constrained stabilized state. 21.The method of claim 20 wherein providing the endovascular stent graftcomprises providing the endovascular stent graft wherein abutting flatsides of the enlarged portions are perpendicular to the longitudinalaxis and parallel to each other so as to prevent slippage by each other.22. An endovascular stent graft, comprising: a main body portionincluding at least one tubular portion made from at least one layer offlexible material; and a self-expanding anchor member which includes: anaxial length, a constrained state, a relaxed expanded state, a pluralityof tapered struts, each one of the plurality of tapered strutscomprising: a proximal crown including a proximal end portion comprisinga first dimension; a distal crown including a distal end portioncomprising a second dimension, the distal end portion positionedopposite the proximal end portion; and a middle portion positionedapproximately halfway between the proximal end portion and the distalend portion, the middle portion extending between and connecting theproximal end portion with the distal end portion, the middle portioncomprising a third dimension that is smaller than the first dimensionand the second dimension, wherein at least one of the plurality oftapered struts tapers continuously from the proximal end portion to themiddle portion, and from the distal end portion to the middle portion; aproximal stent portion having an axial length, a plurality of resilientstruts comprising the plurality of tapered struts, the plurality ofresilient struts configured to exert an outward radial force when in theconstrained state resulting from confinement of the stent inside anouter sheath, with two or more of the plurality of resilient struts thatare non-adjacent to each other having an enlarged portion which isconfigured to stabilize the plurality of resilient struts while thestent is in the constrained state, and at least one resilient strut ofthe plurality of resilient struts is absent the enlarged portion andinterposed between the non-adjacent resilient struts having the enlargedportion, the at least one resilient strut absent the enlarged portioncomprises a first resilient strut absent the enlarged portion and asecond resilient strut absent the enlarged portion that each comprisesone or more barbs extending away from the enlarged portion of one of thetwo or more of the plurality of resilient struts that is adjacent toboth the first and second resilient struts absent the enlarged portion;and a distal stent portion with a proximal end of the distal stentportion secured to a distal end of the proximal stent portion and adistal end of the distal stent portion secured to a proximal end of themain body portion, and wherein the axial length of the self-expandinganchor member as a whole divided by the axial length of the proximalstent portion is 1.75 to 1.9.
 23. The endovascular stent graft of claim22 wherein the main body portion comprises a bifurcated main bodyportion.
 24. The endovascular stent graft of claim 22 wherein theself-expanding anchor member comprises a substantially cylindricalconfiguration.
 25. The endovascular stent graft of claim 22 wherein theself-expanding anchor member comprises a superelastic alloy.
 26. Theendovascular stent graft of claim 25 wherein the superelastic alloy ofthe self-expanding anchor member comprises NiTi.
 27. A self-expandinganchor member, comprising: an axial length, a constrained state, arelaxed expanded state, a proximal stent portion having an axial length,a plurality of tapered struts, each one of the plurality of taperedstruts comprising: a proximal crown including a proximal end portioncomprising a first dimension; a distal crown including a distal endportion comprising a second dimension, the distal end portion positionedopposite the proximal end portion; and a middle portion positionedapproximately halfway between the proximal end portion and the distalend portion, the middle portion extending between and connecting theproximal end portion with the distal end portion, the middle portioncomprising a third dimension that is smaller than the first dimensionand the second dimension, wherein at least one of the plurality oftapered struts tapers continuously from the proximal end portion to themiddle portion, and from the distal end portion to the middle portion; aplurality of resilient struts comprising the plurality of taperedstruts, the plurality of resilient struts configured to exert an outwardradial force when in the constrained state resulting from confinement ofthe stent inside an outer sheath, with two or more of the plurality ofresilient struts that are non-adjacent to each other having an enlargedportion which is configured to stabilize the plurality of resilientstruts while the stent is in the constrained state, and at least oneresilient strut of the plurality of resilient struts is absent theenlarged portion and interposed between the non-adjacent resilientstruts having the enlarged portion, the at least one resilient strutabsent the enlarged portion comprises a first resilient strut absent theenlarged portion and a second resilient strut absent the enlargedportion that each comprises one or more barbs extending away from theenlarged portion of one of the two or more of the plurality of resilientstruts that is adjacent to both the first and second resilient strutsabsent the enlarged portion; and a distal stent portion with a proximalend of the distal stent portion secured to a distal end of the proximalstent portion, and wherein the axial length of the self-expanding anchormember as a whole divided by the axial length of the proximal stentportion is 1.75 to 1.9.
 28. The self-expanding anchor member of claim 27wherein the self-expanding anchor member comprises a substantiallycylindrical configuration.
 29. The self-expanding anchor member of claim27 wherein the self-expanding anchor member comprises a superelasticalloy.